Polarization dynamics of ultrafast solitons

TL;DR

This paper investigates the polarization dynamics of ultrafast solitons in mode-locked fiber lasers, revealing how soliton stability, power levels, and interactions influence polarization states, stability, and soliton behavior through experiments and numerical simulations.

Contribution

It provides new insights into the polarization behavior and stability of ultrafast solitons, supported by experimental data and a non-Lagrangian numerical model.

Findings

Stable solitons shift polarization toward a stable state.

Excess power causes relaxation oscillations in solitons.

Solitons attract and merge, aligning polarization before collision.

Abstract

We study the polarization dynamics of ultrafast solitons in mode-locked fiber lasers. We find that when a stable soliton is generated, it's state-of-polarization shifts toward a stable state and when the soliton is generated with excess power levels it experiences relaxation oscillations in its intensity and timing. On the other hand, when a soliton is generated in an unstable state-of-polarization, it either decays in intensity until it disappears, or its temporal width decreases until it explodes into several solitons and then it disappears. We also found that when two solitons are simultaneously generated close to each other, they attract each other until they collide and merge into a single soliton. Although, these two solitons are generated with different states-of-polarization, they shift their state-of-polarization closer to each other until the polarization coincides when they collide. We support our findings by numerical calculations of a non-Lagrangian approach by simulating the Ginzburg-Landau equation governing the dynamics of solitons in a laser cavity. Our model also predicts the relaxation oscillations of stable solitons and the two types of unstable solitons observed in the experimental measurements.